c Pipe Material Behaviour Didier Ilunga Only]
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Transcript of c Pipe Material Behaviour Didier Ilunga Only]
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DIDIER ILUNGA
Prof JE VAN ZYL &
Dr M. DUNDU
THE EFFECT OF THE PIPE MATERIALIN THE BEHAVIOUR OF
LONGITUDINAL CRACKS UNDER
PRESSURE
SERVICES (PTY) LTD
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INTRODUCTION Problem of leakage
Leakage much more sensitive to pressure
Theoretically, =0.5,
In the field, 0.5 2.8
ghACQ d 2=
( )5.0
.2 == hgACQ d
SERVICES (PTY) LTD
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Pipe material behaviour
Longitudinal cracks in water pipes
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OBJECTIVES Investigate and understand the structural
behaviour of longitudinal crack in pipe with
increasing pressure
Derive an Equation for crack opening area
-Pressure
-Material properties
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OBJECTIVES Derive an Equation for leakage flow through a
longitudinal crack in uniaxial stress state (used
as model)-Geometry of the pipe
-Pipe material
-Fluid properties
Predict an appropriate leakage Equation forpressurised pipes
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Based on
-Theoretical approach
-Experimental verification on flat plate
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Stresses in pressurised cylinders
STRESSES IN PRESSURISED THIN-
CYLINDERS
)(2)(1 2 AxialHoop =
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Behaviour of Crack due to Internal Pressure
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MECHANICAL EXPLANATION
Stress concentration around crack edges Hoop stresses dominate
Pressure assists with pushing walls open
Curvature of the pipe
Cause bulging on crack faces
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Y
x
tL
W
2aNy
Ny
Rectangular cracked thin-plate under tension
THEORETICAL APPROACH
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Apply tensile load on the plate material
Measure the resulting the strain
deformations until the crack startspropagating
EXPERIMENTAL APPROACH
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Local buckling and crack opening
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MAXIMUM CRACK OPENING AREA IN APLATE
Assuming no crack propagation, the altered
shape of the crack
2a yu
a
xa
E
Ku y
224 =
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0max, =xuy
axuy =min,
maxyu
a
maxyu
0 x
0max, =xuy
a
E
K
u y
4
max=
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RESULTS
Crack Opening Area, function of Critical
buckling load of the plate in uniaxial stress state
+= tE
vNauA crycry 1.
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+=
tE
RghvauA cr
cry
1.
Crack Opening Area, function of Critical Pressure
and Material Properties within a pressurised Pipein uniaxial stress state
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( )212
3
2
1
2. gtE
gRhvhauCQ
ydactual
+=
Derived Equation for flow leakage through a
longitudinal crack function of Pressure, MaterialProperties, Pipe geometry and Fluid Properties
within a pressurised Pipe in uniaxial stress state
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Effect of Pressure on Leakage flow due to
expansion of the Crack
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LOSS ESTIMATION
6.185 l/s at 17 bar
534384 l/day
R 2404728/day
R 72141840/month
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DISCUSSION
Effect of the opening is more important the
longer the crack is
Buckling mode of the crack in plate issimilar to the Bulging mode of a
longitudinal crack in pressurised pipe
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SUMMARY
Material around the crack bulges out
Increase of the leak area due pressure
Leakage exponents are considerably
larger than 0.5 and increase as the crack
area expands.
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ACKNOWLEDGEMENTS
This project research wishes to gratefully
acknowledge the financial support fromRand Water.
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THANK YOU